Fci, Inc.

Sung Ho Beck

Myung Woon Hwang

A variable gain amplifier (VGA) with a linear-in-dB gain characteristic is provided. The VGA includes: a control signal converter which converts an input gain control signal V, which is input so that the VGA obtains a linear-in-dB gain characteristic to the maximum gain, into an output gain control signal V=Vln((1/m)exp(&#x2212;V/V)&#x2212;1) (m is a constant, V=kT/q); and a variable gain amplifier which receives and converts the output gain control signal Voutput from the control signal converter so that the gain has a linear-in-dB characteristic. A shape of a gain curve is externally controlled.

Variable gain amplifier having linear-in-dB gain characteristic

The mixer includes mixers constructed with variable gain amplifiers having two transistor pairs Qp+/Qp&#x2212; and Qn+/Qn&#x2212; to have a predetermined gain by using LO+ and LO&#x2212; signals; and LO bias circuits connected to have bias voltages different from each other with respect to the LO+ and LO&#x2212; signals of the mixers and share an input signal.

Variable gain mixer

Provided is a low-power variable gain amplifier having a direct-current (DC) bias stabilizer. The low-power variable gain amplifier includes: a load block through which first and second load currents flow from a first source voltage; a first differential input signal source including a terminal connected to a second source voltage and the other terminal connected to a variable gain amplifying block and sinking currents corresponding to a value of a first differential input current signal; a second differential input signal source including a terminal connected to the second source voltage and the other terminal connected to the variable gain amplifying block and sinking currents corresponding to a value of a second differential input current signal; a variable gain amplifying block sinking first and second differential output current signals that are branch currents of the first and load currents, respectively, and first and second destructive-compensation current signals, in response to first and second gain control signals and the first and second differential input current signals; and the DC bias stabilizer processing the first and second destructive-compensation current signals and first and second bias currents that are branch currents of the first and second load currents, respectively, to enable the first and second load currents to include fixed DC current components, wherein the currents sunk to the first and second differential input signal sources include DC current components and AC current components, the DC current components of the first and second differential input signal sources have the same value, and the AC current components thereof have a phase difference of 180&#xb0;.

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Seongnam-si, South Korea

Sung Ho Beck